More TDA7052 Amplifier Developments - 2

Small Stereo Portable amplifier

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This system is just a small stereo amplifier only. It uses two TDA7052 chips,
notes are available on this chip here. It has a small plug that
can accept most DC adaptors or a battery back (which I have built many of, e.g.
for the above project). The line input is in the form of a stereo 3.5mm jack socket
(which is the most useful) and it has two phono sockets for the amplified output.

The primary need for it is something simple just to power my rear speakers
for a small surround sound application in my own room. It can also serve as a
good audio system to plug my laptop into when I am laying in bed. It needs some
power, but also needs to be small and portable (well I wanted it to be anyway).
Of course making it look good too would be an added bonus.

The box itself is a very small box, which is a nice translucent blue. It is
100mm long, 50mm wide and 25mm deep at its external extremes. The PCB is just
18.5mm x 95mm and houses tow TDA7052 amps, a dual volume control, a stereo jack
input socket, and LED and a 2.1mm DC power socket. From the picture above, you
can see all that was included in my order. The board has been cut and drilled,
but not designed yet and is just to the left of the box. Far left is the paper
design of the board I used as a template to get all the holes and tracking
correct. I'm going to talk a little about making the PCB here, but for more in
depth information on how I do it, take a look at my
PCB building guide. After drilling and cutting, here is the PCB after I have
carefully drawn on the tracks (its a work of art)

Once that is dry, etching must commence. As always, I was careful
about using the etchant as it is toxic and corrosive.

After about half an hour or more, the etching process was complete. It took a
while because I am assuming my etchant is running low.

You can see the difference in the colour of the board now, that is because
all the exposed copper has been removed by the etchant. The only bit remaining
is the bit at the bottom. The reason for this is the nature of the ferrite
chloride solution deposit iron as it removes the copper. That means I have a
layer of iron at the bottom of this jar which was preventing the copper from
being etched. This bottom area of the PCB was the only part resting on the
bottom of the jar as I suspended the rest of the board by using cotton thread,
which you can see (it is red). This is a good idea as it prevents things from
getting messy. Once the PCB was cleaned and the etch resist pen was removed, the
result is below:

While I waited for the etching to be done, I started work on drilling the
box. I got a total of two holes done as I found I spent a lot of time modifying
the phono sockets so they would fit in the box snugly. With the phono sockets
nearly in place (need to be screwed down yet) and the board soldered up with
components, here is the two together:

The board looks rather nice from above and you can see that the whole design
has minimal wire use, 6 in total. Its easy to spot that there are two TDA7052
amp circuits there by the simple fact that the middle part of the board is
similar to the left. Differences being that there is an LED and its resistor in
the middle, and on the far left is the DC power socket and protection diode. The
switch is a simple slide switch that cuts of the negative voltage. You can also
see from the picture how I had to cut and file the phono socket board to get it
to fit in the box.

The back shows the neat soldering job and how the wires are connected to the
power switch and the phono sockets. Its very simple hock ups indeed.

On testing, so far, the amplifier worked with both channels perfectly first
time. Absolutely no mishaps at all, which is always makes a guy happy :-D

I couldn't do volume testing or anymore drilling that evening because my
housemate went to sleep early. Late the next day, I decided to finish it, and
did so successfully. Below are 2 views of the amplifier complete, plugged in and
working at the time of the photos.

You can see that is is actually a small and neat little design. Power input
is on the side and a rather large slide switch is mounted on the top (only just
fit). Next to that is a lovely blue LED and then there is the volume control
followed by the 3.5mm jack input socket. On the side above the volume control is
the two phono sockets as shown in previous pictures.

From the bottom, there is a clearer view of the circuitry that makes it all
work :)

Plugged into a decent set of stereo speakers, it shows promising capabilities
with good tonal response. There is a little bit of hum unfortunately, but I am
blaming that on the Â£1 multi-voltage PSU from the boot sale. Otherwise, its
application is already in use as a better music system for my laptop. I shall
hook up the surround sound decoder another time.

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